Vibratory conveyors and shakers are commonly used for dewatering, separating and grading various material, such as for example fruits and vegetables. Conventionally, such conveyors comprise a working conveyor bed mounted to a frame, and a vibratory exciter arranged to impart vibrating motion to the conveyor bed. The conveyor bed is provided with a screen deck which is conventionally a rigid apertured bed made up of a plurality of screening panels. The screening panels are removably mounted to the conveyor bed frame such that different mesh panels can be substituted depending upon the material being processed, and for replacement of the screens upon excessive wear. A great challenge in the design and maintenance of such conveyors is to provide a bed which enables the screen panels to be rigidly held in place relative to the conveyor bed, and yet easily removed when one desires to change a screen.
One existing prior art method for maintaining the screen panels in their desired positions relative to a conveyor bed is illustrated in FIG. 3. FIG. 3 is a vertical and partial section view of a conveyor bed 10 illustrating a screen panel 12 being clamped relative thereto by a prior art clamping device 14. The product being processed and conveyed by conveyor bed 10 would move into the page upon which FIG. 3 appears. Clamp 14 is vertically oriented, and the vibratory drive (not shown) would vibrate bed 10 and screens 12 upwardly and forwardly at an inclined angle generally into the direction of the page. Clamp 14 includes a hook member 16 which is pivotally mounted relative to a lever arm 18 and a mounting base 20 for imparting a vertically downward clamping force against screen 12. Screen 12 is clamped vertically downward against an inner side rail 36 of conveyor bed 10.
More particularly, mounting base 20 is welded or otherwise secured to the external surface of conveyor bed frame 10. Base 20 pivotally supports lever arm 18 relative thereto at one of the lever arm ends for pivoting about a horizontal axis 22. Hook member 16 is also pivotally mounted relative to lever arm 18 by a horizontal pivot rod 24. Hook 16 is threaded at its lower end and threadably receives a tension adjustable nut 28. A tension spring 26 is received between pivot rod 24 and nut 28.
The upper hooking portion of hook member 16 is received through a side opening 30 which is formed in conveyor bed frame 10. Opening 30 is elongated in the vertical direction to accommodate the insertion and removal of hook 16 therethrough the result of the vertical arcing movement of the upper portion of hook 16 by pivot action about pivot axis 22. This would otherwise create a large opening in the side of conveyor bed 10 through which some of the material being processed would fall to the ground and be lost. To eliminate this loss of product, a bent metal guard 32 is affixed to the internal surface of conveyor bed frame 10 and covers opening 30. Guard 32 is secured to frame 10 at its upper end and includes an upwardly angled portion 34 at its lower end against which hook 16 bears. This lower portion 34 is slidable relative to bed frame 10 such that a clamping force applied against lower portion 34 will be transmitted vertically downward onto screen 12. Guard 32 and the position of hook 16 provide a disadvantage of projecting into the processing path of the material being conveyed. This reduces the effective width of the processing bed.
Typically, two of such clamps would be provided on each side of each individual screen panel of a conveyor bed. A camming-lock clamping action is provided by lever arm 18 and pivot rod 24 relative to mounting block 20. A locking clamp force is provided by camming action when pivot rod 24 is rotated to a location beneath an imaginary line 38 defined by the tip of clamp hook 16 and pivot axis 22.
Such conveyor beds are not without disadvantages. For example, the excessive vibratory force necessary to impart the conveying action has been found on occasion to cause mounting blocks 20 to separate relative to conveyor bed frame 10. Further, the downward clamping force must be large as it must clamp the screen relative to the bed which is being vibrated with a force having another directional component. Further, the orientation of hook 16 and guard 32 relative to conveyor bed 10 reduces the effective width of the processing conveyor, as previously described.